Multipawl feed mechanism



April 1952 s. AIJALA 2,591,993

MULTIPAWL FEED MECHANISM Filed Oct. 7, 1947 2 SHEETS-SHEET 1 April 8, 1952 s. AIJALA 2,591,993

MULTIPAWL FEED MECHANISM Filed 001;. 7, 1947 2 swam-swam z Patented Apr. 8, 1952 MULTIPAWL FEED MECHANISM Sulo Aijala, Coventry, R. L, assignor to Carl G. Peterson (30., a corporation of Rhode Island Application October 7, 1947, Serial No. 778,381

a feed mechanism which uses a large number of pawls, set to provide feeds accurate to two thousandths of an inch. I r 1 Still another object is to provide a simple feed mechanism which has a small number of readily manufactured and assembled parts. 1

With the above and other objects and advantageous featuresin view, the invention consists of a novel arrangement of parts more fully disclosed in the detailed description following, in conjunction with the accompanying drawings. and more specifically defined in the claim appended thereto.

In the drawings:

Fig. 1 is an elevation of a feed mechanism embodying the invention;

Fig. 2 is a top plan view of Fig. 1;

Fig. 3 is a partial section on the line 3--3 of Fig. 1;

Fig. 4 is an enlarged detail of the ratchet parts;

Fig. 5 is a perspective view of one ratchet pawl; and

Fig. 6 is a perspective exploded view of the removable hub mounting for the feed roll shaft.

It has been found desirable to provide an accurate feed mechanism for the feed rollsof a stamping press, punch press and the like, which is positive in action, has no back lash, and is accurate to at least two-thousandths of an inch. To this end, I have devised a simple feed mechanism made of a small number of easily manufactured and readily assembled parts, which utilizes a main ratchet wheel and a large number of catch pawls so arranged that they progressively engage the teeth of the ratchetwheel for exact increments of feed travel.

Referring to the drawings, the feed mechanism It) includes an outer housing H which may be made of transparent plastic if desired, and which has a front face plate l2, a rear face plate I3, and an annular shell M which is locked between the face plates to provide an annular compartment IS. The face plates have aligned extensions I6, I! which receive a cross rod l 8 on which a standard lever from the stamping press eccentric is pivotally mounted, whereby the housing is inter- 1 Claim. (Cl. 74-577) the hub having a fixed collar 20 at one end and a removable collar 2| at the other end, which seat against the outer surfaces of the face plates. A ratchet wheel 22 is keyed to the hub I9 and is housed between the face plates in the compartment l5, as shown in Fig. 2, the periphery of the wheel having'a multiplicity of transverse ratchet teeth 23.

A series of pawls 24 within the compartment l 5 are eccentrically pivotally mounted on spaced cross studs-25 which are locked in the two face plates. the studs 25 being circularly positioned in the face plates as shown in Fig. 1. Each pawl is of block type and its forward portion 26 has a depending 'acatch tooth or edge 21 to selectively engage the ratchet teeth 23, and each pawl has an upstanding. projection 28 which is grooved as indicated by} the reference numeral29; the pawls are arranged gin two adjacent annular sets 30, 3|, see FigLf'Z'," whereby coil springs 32, 33 may extend circularly over the pawl projections 21 and seat in thegrooves 29 to resiliently press the forward portionsZB downwardly into engagement with the ratchet teeth 23.

As the face plates are intermittently turned in response to movement of stamping press eccentric, the pawls also move to turn the ratchet wheel, which turns the hub and the feed roll shaft keyed therein; the pawl teeth thus accurately and positively move the ratchet wheel forwardly with no back lash and with extreme accuracy.= I

The accuracy of the feeding movement is controlled by the number and the setting of the pawls which selectively lock with the ratchet wheel to produce the desired exact forward movement. Ihe shortest possible feed depends on the diameter of the feed rolls, the number of pawls, and the number of teeth of the ratchet wheel, in accordance with the formula wherein F is the feed interval, which may vary by as little as .0009 inch, d the diameter of the feed rolls, which may be 2, 3 or 4 inches, for example, P the total number of pawls, and T is the number of teeth in the ratchet wheel.

The setting of the pawl studs is determined by the formula 360 T 360 r-Wm;

wherein 0 is the angular distance between adjacent pawl studs, N is the total number of pawl studs for the feed, and

is a whole number, dropping the fraction if any. The dropping of the fraction is necessary to provide clearance, and ensures a substantially complete utilization of the pawl stud circle. The linear distance from center to center between pawl studs isdetermined-by the formula as r 360 wherein S is the linear distance between pawl studs and R is the radius of the pawl, and circle,

and

S=2R sin 21rR' TP where Q is, the difference in set settings.

A larger number of adjacent sets of pawls may be used to obtain still smaller feed increments. Where more than two sets of adjacent pawls are desired it is preferred to provide anumber of separate ratchet disks, which should be machined together toinsureexact tooth registration, and to displace thedisks according to the calculated difference in set settings; this construction has the advantage that the-pawls are oi identical size and are interchangeable.

The invention thus provides a multi-pawl feed mechanism which is adapted tobe periodically actuated or oscillated by an eccentric.of standardtype, the feed mechanism consisting. of a housing in which a ratchet wheel is rotatably mounted, the ratchet wheel being provided with peripheral teeth which are selectively engaged by an annular series of pawls, the pawls beingtaining the size of the feed mechanism within practicable limits. Thus, the feed mechanism for obtaining a feed with the described accuracy need not be over six inches in overall diameter, and'one and one-half inches in width, whereby it is readily mounted on small presses.

Although I have described a specific embodiment' of'the invention, it is obvious that changes in the novel arrangement of parts may be made tosuit the requirements for diiierent multipawl feed mechanism, without departing from thespirit and the scope of the invention as defined in the appended claim.

I claim:

In a multi-pawl feed mechanism, a. housing comprising. a front plate, a rear plate spaced therefrom, and anannular shell locked. between said plates, said plates having aligned extensions, a cross rod between said extensions adapted to be oscillated, a-hub rotatably mounted in said-plates and adapted to receive a shaft, a ratchet wheelkeyed to said hub having aplurality of transverse ratchet teeth on the periphery. thereof, cross studs locked to the plates positioned between said ratchet wheel and the annular shell, pawls pivotally mounted on said studs and having teeth at their forward ends for engagement with the ratchet teeth, said pawls having upstanding projections on said forward ends provided with spring receivinggrooves, and

an annular coil spring seated in said grooves and resiliently urging the forward ends of the pawls towards the ratchet wheel.

SULO AIJALA.

REFERENCES CITED The following references are of record in the file of thispatent:

UNITED STATES PATENTS 

